The present invention pertains to a distributed architecture for all aerial navigation aids.
To ascertain its location in flight, with respect to fixed points on the ground, an aircraft receives a certain number of signals transmitted by beacons situated at these points. These signals make it possible to designate either the distance to the fixed point, or an orientation in the horizontal plane tangent to the earth and containing this point, or an orientation with respect to its local vertical. To process these signals, the aircraft is equipped with a constellation of antennas, linked by coaxial cables to dedicated receivers, the latter being installed in an electronic rack close to the flight deck.
Represented in FIG. 1 is a simplified example of the disposition of the antennas relating to the aerial navigation aid equipment of an aircraft 1. These antennas are, in this example, those relating to the following equipment: GPS (two antennas), ADF (“Automatic Direction Finder”, also with two antennas), ELT (“Energy Locator Transmitter”), VOR, ILS-GS (“ILS-Glide Slope”), ILS-LOC (“ILS Localizer”), DME-1 and DME-2 (“Distance Measuring Equipment”), MB (“Marker Beacon”) and Radio-altimeter (four antennas in total, namely two for transmission and two for reception). All these antennas are linked by coaxial cables to corresponding transmitter and/or receiver equipment clustered together in the electronic rack 2.
The part of the electronic rack 2 relating to the radionavigation equipment has been schematically represented. This equipment is: the VOR-1 and 2 receivers, the DME-1 and 2 transmitters-receivers, the ILS-LOC and GS 1 and 2 receivers, the ADF 1 and 2 receivers, and the GPS 1 and 2 receivers. The digital interfaces (not represented) of these transmitters and receivers are linked by a digital bus 3 to a central computer 4. The various transmitters and receivers are linked by coaxial cables (denoted “coax” in the drawing) to the corresponding antennas.
The processing of the navigation signals by the receivers is manifested, inter alia, in the form of visual indications (dials, screens, counters, lights) and audible indications (Morse codes transmitted by the beacons and constituting their signatures).
The specific drawback of this architecture is that the electronic rack takes up a great deal of room, and that the aircraft is traversed by a large number of coaxial cables, which themselves represent a large volume and especially a significant mass. These cables are moreover expensive, since they are chosen so as to exhibit minimum losses in the transport of information and to have very effective shielding against electromagnetic disturbances.
Part of the problem can be solved by replacing the coaxial cables with links based on optical fibers, but though this makes it possible to decrease the weight and volume of the cables, it does not solve the problem of the volume of the electronic rack and requires the installation of components whose integrity level is not well known in the field of onboard aeronautics.
Another factor influencing the weight is that each receiver, today, has its own power supply, that is to say a DC/DC electrical converter making it possible to produce on the basis of the energy provided by the aircraft ( 19/37 VDC) all the DC voltages (±10V, ±15V, ±5V, 3.3V) that are required in order to operate.